The present invention relates generally to fastener-driving tools used to drive fasteners into workpieces, and specifically to combustion-powered fastener-driving tools, also referred to as combustion tools.
Combustion-powered tools are known in the art, and one type of such tools, also known as IMPULSE® brand tools for use in driving fasteners into workpieces, is described in commonly assigned patents to Nikolich U.S. Pat. Re. No. 32,452, and U.S. Pat. Nos. 4,522,162; 4,483,473; 4,483,474; 4,403,722; 5,197,646; 5,263,439 and 6,145,724, all of which are incorporated by reference herein. Similar combustion-powered nail and staple driving tools are available commercially from ITW-Paslode of Vernon Hills, Ill. under the IMPULSE®[ ] and PASLODE® brands.
Such tools incorporate a tool housing enclosing a small internal combustion engine. The engine is powered by a canister of pressurized fuel gas, also called a fuel cell. A battery-powered electronic power distribution unit produces a spark for ignition, and a fan located in a combustion chamber provides for both an efficient combustion within the chamber, while facilitating processes ancillary to. Such ancillary processes include: inserting the fuel into the combustion chamber; mixing the fuel and air within the chamber; and removing, or scavenging, combustion by-products. The engine includes a reciprocating piston with an elongated, rigid driver blade disposed within a single cylinder body.
Upon the pulling of a trigger switch, which causes the spark to ignite a charge of gas in the combustion chamber of the engine, the combined piston and driver blade is forced downward to impact a positioned fastener and drive it into the workpiece. The piston then returns to its original, or pre-firing position, through differential gas pressures within the cylinder. Fasteners are fed magazine-style into the nosepiece, where they are held in a properly positioned orientation for receiving the impact of the driver blade.
Conventional combustion fastener driving tools employ straight magazines holding approximately 30 fasteners each. In some operational applications, particularly commercial construction projects, there is a need for a tool which is capable of driving a greater number of fasteners in a shorter period of time. The use of coil magazines with greater fastener capacities is common in electrically or pneumatically powered fastener driving tools, but for various reasons, such magazines have not become acceptable with combustion tools. Reasons for the undesirability of such high capacity magazines in these tools include the additional weight of the fasteners causing premature operator fatigue, and the additional energy required to operate the coil magazine fastener advance has not proved reliable.
Aside from the size of the magazine of conventional combustion tools, the weight, balance and overall ergonomics of conventional tools have not been suitable for high volume commercial construction applications, among others. In addition, when more rapid firing rates are contemplated for such tools, care must be taken to ensure that at the conclusion of each firing cycle, the piston returns to its prefiring position before the next firing cycle begins. Failure of the piston to properly return has been known to cause tool jams and other operational difficulties.
Thus, there is a need for a combustion-powered fastener-driving tool which is capable of operating reliably with high capacity magazines, including but not limited to coil magazines. There is also a need for a combustion-powered fastener-driving tool which is designed for driving fasteners from such a magazine at a relatively high rate.